Email Address Internationalization K. Fujiwara
(EAI) JPRS
Internet-Draft February 15, 2008
Intended status: Experimental
Expires: August 18, 2008
Displaying Downgraded Messages for Email Address Internationalization
draft-fujiwara-eai-downgraded-display-00.txt
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on August 18, 2008.
Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract
This document describes how to display downgraded messages which
originally contain internationalized E-mail addresses or
internationalized header fields.
Fujiwara Expires August 18, 2008 [Page 1]
Internet-Draft Displaying Downgraded Messages February 2008
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Displaying downgraded message . . . . . . . . . . . . . . . . 4
3.1. Displaying technique 1 . . . . . . . . . . . . . . . . . . 4
3.2. Displaying technique 2 . . . . . . . . . . . . . . . . . . 4
4. Security considerations . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
7. Change History . . . . . . . . . . . . . . . . . . . . . . . . 6
7.1. draft-fujiwara-eai-downgraded-display: Version 00 . . . . 6
8. Normative References . . . . . . . . . . . . . . . . . . . . . 6
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 7
A.1. Displaying technique 1 example . . . . . . . . . . . . . . 10
A.2. Displaying technique 2 example . . . . . . . . . . . . . . 10
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 13
Intellectual Property and Copyright Statements . . . . . . . . . . 14
Fujiwara Expires August 18, 2008 [Page 2]
Internet-Draft Displaying Downgraded Messages February 2008
1. Introduction
The Email Address Internationalization (UTF8SMTP) extension document
set [RFC4952] [I-D.ietf-eai-smtpext] [I-D.ietf-eai-utf8headers]
[I-D.ietf-eai-dsn] expands Email address structure, syntax and Email
header format. To avoid bouncing internationalized Email messages,
the downgrading mechanism [I-D.ietf-eai-downgrade] converts an
internationalized message to a traditional Email message when a
server in the delivery path does not support the UTF8SMTP extension.
The downgraded message is a traditional Email message, except the
message has "Downgraded-" header fields.
A perfect reverse-function of the downgrading does not exist because
the encoding defined in [RFC2047] is not exactly reversible and
Received header field downgrading may remove FOR clause information.
The restoration of the downgrading should be done once at the final
destination of the downgraded message such as MUAs or IMAP servers.
This document describes the restoration methods as displaying
techniques in MUAs.
This is an informational document and it does not supersede the
referenced documents.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Specialized terms used in this specification are defined in the EAI
overview [RFC4952] or in [RFC2821][RFC2822], MIME documents [RFC2045]
[RFC2047] [RFC2183] [RFC2231].
This document depends on [I-D.ietf-eai-utf8headers] and
[I-D.ietf-eai-downgrade]. Key words used in these document are used
in this document, too.
The term "non-ASCII" is an UTF-8 string which contains at least one
non-ASCII character.
The term "address header field" is used for a header field which
contains <mailbox> elements which is defined in [RFC2822]. "Address
header fields" contain "From", "Sender", "Reply-To", "To", "Cc",
"Bcc", "Resent-From", "Resent-Sender", "Resent-To", "Resent-Cc",
"Return-Path" header fields.
An "UTF8SMTP message" is an Email messages expanded by
Fujiwara Expires August 18, 2008 [Page 3]
Internet-Draft Displaying Downgraded Messages February 2008
[I-D.ietf-eai-utf8headers].
3. Displaying downgraded message
Displaying downgraded message is mostly performed by MIME decoding
according to [RFC2047] and [RFC2231]. Result of MIME decoding, the
header of the message still contains Downgraded-*: header fields, but
the header field bodies are MIME decoded. These decoded
"Downgraded-" header fields contain the original header field name
and the original header field values. The recipient can read them.
But the recipient's MUA cannot use the original header fields
automatically.
Additionally, MUAs can process "Downgraded-" header fields. It is
described in Section 3.1 and Section 3.2.
3.1. Displaying technique 1
MUAs may remove "Downgraded-" from decoded "Downgraded-" header
fields' name.
First, decode MIME encoded header fields and MIME body part header
fields according to [RFC2047] and [RFC2231].
Then, for each "Downgraded-" header field, generate new header field
which field name is the original header field name and the field
value is the decoded header field value, and replace the
"Downgraded-" header field by the generated header field.
Don't change "Downgraded-Mail-From" and "Downgraded-Rcpt-To" header
fields because they do not have their original header fields.
With this technique, the "address header fields" may be displayed
twice, one is from downgraded header field and the other is from
decoded "Downgraded-" header.
3.2. Displaying technique 2
MUAs may decode and re-generate the original header of the message.
This technique may reconstruct the original message from the
downgraded message. But it is not guaranteed.
This technique is implemented by the following steps.
Fujiwara Expires August 18, 2008 [Page 4]
Internet-Draft Displaying Downgraded Messages February 2008
Step 1: Select "Downgraded-" header fields whose original header
field is an "address header field". Target header fields are
"Downgraded-From", "Downgraded-Sender", "Downgraded-Reply-To",
"Downgraded-To", "Downgraded-Cc", "Downgraded-Bcc", "Downgraded-
Resent-From", "Downgraded-Resent-Sender", "Downgraded-Resent-To",
"Downgraded-Resent-Cc", and "Downgraded-Return-Path" header
fields.
Step 2: Generate new header field which field name is the original
header field name and the field value is the decoded header field
value from the output of Step 1.
Step 3: Apply Email header fields downgrading defined in section 5
of [I-D.ietf-eai-downgrade] to the output of Step 2 without re-
generating "Downgraded-" header fields.
Step 4: Compare the output of Step 3 and the original header
fields. If the same header fields exist for both the output and
the original header fields, remove the same header fields from the
original header fields. This step outputs the original header
fields which is modified by this step. Before this comparison, a
canonicalization described below is useful.
1. Unfold all header field continuation lines as described in
[RFC2822].
2. Insert a space character before and after <mailbox-list>
separator "," if there is no space character.
3. Insert a space character before and after <comment> if there
is no space character.
4. Decode <encoded-word> whose charset is 'UTF-8'.
5. Convert all sequences of one or more WSP characters to a
single space character. WSP characters here include those
before and after a line folding boundary.
6. Delete all WSP characters at the end of each unfolded header
field value.
7. Delete any WSP characters remaining before and after the colon
separating the header field name from the header field value.
The colon separator MUST be retained.
Step 5: Finally, do 'Displaying technique 1' described in
Section 3.1 to the output of Step 4.
4. Security considerations
Displaying downgraded message may break the header of the message.
MUAs should have a function to read the original received message.
Fujiwara Expires August 18, 2008 [Page 5]
Internet-Draft Displaying Downgraded Messages February 2008
See "Security considerations" section in [RFC4952] for more
discussion.
5. IANA Considerations
6. Acknowledgements
7. Change History
This section is used for tracking the update of this document. Will
be removed after finalize.
7.1. draft-fujiwara-eai-downgraded-display: Version 00
o Initial version
o It is separated from Appendix A of draft-ietf-eai-downgrade-05.txt
8. Normative References
[I-D.ietf-eai-downgrade]
Yoneya, Y. and K. Fujiwara, "Downgrading mechanism for
Email Address Internationalization",
draft-ietf-eai-downgrade-06 (work in progress),
February 2008.
[I-D.ietf-eai-dsn]
Newman, C. and A. Melnikov, "Internationalized Delivery
Status and Disposition Notifications",
draft-ietf-eai-dsn-06 (work in progress), January 2008.
[I-D.ietf-eai-smtpext]
Yao, J. and W. MAO, "SMTP extension for internationalized
email address", draft-ietf-eai-smtpext-11 (work in
progress), January 2008.
[]
Yeh, J., "Internationalized Email Headers",
draft-ietf-eai-utf8headers-09 (work in progress),
February 2008.
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, November 1996.
Fujiwara Expires August 18, 2008 [Page 6]
Internet-Draft Displaying Downgraded Messages February 2008
[RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions)
Part Three: Message Header Extensions for Non-ASCII Text",
RFC 2047, November 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2183] Troost, R., Dorner, S., and K. Moore, "Communicating
Presentation Information in Internet Messages: The
Content-Disposition Header Field", RFC 2183, August 1997.
[RFC2231] Freed, N. and K. Moore, "MIME Parameter Value and Encoded
Word Extensions:
Character Sets, Languages, and Continuations", RFC 2231,
November 1997.
[RFC2821] Klensin, J., "Simple Mail Transfer Protocol", RFC 2821,
April 2001.
[RFC2822] Resnick, P., "Internet Message Format", RFC 2822,
April 2001.
[RFC4952] Klensin, J. and Y. Ko, "Overview and Framework for
Internationalized Email", RFC 4952, July 2007.
Appendix A. Examples
This section shows a example of displaying downgraded message.
First, an example of the original UTF8SMTP message and its downgraded
message are shown. They are the same as "Example 1" of
[I-D.ietf-eai-downgrade]. The example UTF8SMTP message is shown in
Figure 1.
Fujiwara Expires August 18, 2008 [Page 7]
Internet-Draft Displaying Downgraded Messages February 2008
Message-Id: MESSAGE_ID
Mime-Version: 1.0
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 8bit
Subject: NON-ASCII-SUBJECT
From: DISPLAY-local <NON-ASCII-local@example.com
<ASCII-local@example.com>>
To: DISPLAY-remote1 <NON-ASCII-remote1@example.net
<ASCII-remote1@example.net>>
Cc: DISPLAY-remote2 <NON-ASCII-remote2@example.org>
Date: DATE
MAIL_BODY
Figure 1: Original message
Delivered downgraded message is shown in Figure 2. Return-Path
header will be added by the final destination MTA.
Return-Path: <ASCII-local@example.com>
Downgraded-Mail-From: =?UTF-8?Q?<NON-ASCII-local@example.com>_?=
=?UTF-8?Q?<ASCII-local@example.com>?=
Downgraded-Rcpt-To: =?UTF-8?Q?<NON-ASCII-remote1@example.net>_?=
=?UTF-8?Q?<ASCII-remote1@example.net>?=
Message-Id: MESSAGE_ID
Mime-Version: 1.0
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 8bit
Subject: =?UTF-8?Q?NON-ASCII-SUBJECT?=
From: =?UTF-8?Q?DISPLAY-local?= <ASCII-local@example.com>
Downgraded-From: =?UTF-8?Q?DISPLAY-local_<NON-ASCII-local@example.com_?=
=?UTF-8?Q?<ASCII-local@example.com>>?=
To: =?UTF-8?Q?DISPLAY-remote1?= <ASCII-remote1@example.net>
Downgraded-To: =?UTF-8?Q?DISPLAY-remote1_?=
=?UTF-8?Q?<NON-ASCII-remote1@example.net_<ASCII-remote1@example.net>>?=
Cc: =?UTF-8?Q?DISPLAY-remote2?= Internationalized address
=?UTF-8?Q?NON-ASCII-remote2@example.org?= removed:;
Downgraded-Cc: =?UTF-8?Q?DISPLAY-remote2_?=
=?UTF-8?Q?<NON-ASCII-remote2@example.org>?=
Date: DATE
MAIL_BODY
Figure 2: Downgraded message
Fujiwara Expires August 18, 2008 [Page 8]
Internet-Draft Displaying Downgraded Messages February 2008
Figure 3 shows MIME decoded message of Figure 2. The recipient can
read the original From, To, Cc header fields as Downgraded-From,
Downgraded-To, Downgraded-Cc header fields.
Return-Path: <ASCII-local@example.com>
Downgraded-Mail-From: <NON-ASCII-local@example.com>
<ASCII-local@example.com>
Downgraded-Rcpt-To: <NON-ASCII-remote1@example.net>
<ASCII-remote1@example.net>
Message-Id: MESSAGE_ID
Mime-Version: 1.0
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 8bit
Subject: NON-ASCII-SUBJECT
From: DISPLAY-local <ASCII-local@example.com>
Downgraded-From: DISPLAY-local <NON-ASCII-local@example.com
<ASCII-local@example.com>>
To: DISPLAY-remote1 <ASCII-remote1@example.net>
Downgraded-To: DISPLAY-remote1 <NON-ASCII-remote1@example.net
<ASCII-remote1@example.net>>
Cc: DISPLAY-remote2 Internationalized address
NON-ASCII-remote2@example.org removed:;
Downgraded-Cc: DISPLAY-remote2 <NON-ASCII-remote2@example.org>
Date: DATE
MAIL_BODY
Figure 3: MIME decoded message
Fujiwara Expires August 18, 2008 [Page 9]
Internet-Draft Displaying Downgraded Messages February 2008
A.1. Displaying technique 1 example
After removing "Downgraded-" from decoded "Downgraded-" header fields
from Figure 3, 'Displaying technique 1' example is shown in Figure 4.
Return-Path: <ASCII-local@example.com>
Mail-From: <NON-ASCII-local@example.com>
<ASCII-local@example.com>
Rcpt-To: <NON-ASCII-remote1@example.net>
<ASCII-remote1@example.net>
Message-Id: MESSAGE_ID
Mime-Version: 1.0
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 8bit
Subject: NON-ASCII-SUBJECT
From: DISPLAY-local <ASCII-local@example.com>
From: DISPLAY-local <NON-ASCII-local@example.com
<ASCII-local@example.com>>
To: DISPLAY-remote1 <ASCII-remote1@example.net>
To: DISPLAY-remote1 <NON-ASCII-remote1@example.net
<ASCII-remote1@example.net>>
Cc: DISPLAY-remote2 Internationalized address
NON-ASCII-remote2@example.org removed:;
Cc: DISPLAY-remote2 <NON-ASCII-remote2@example.org>
Date: DATE
MAIL_BODY
Figure 4: Displaying technique 1
A.2. Displaying technique 2 example
This example shows displaying process of 'Displaying technique 2' for
Figure 2.
First, perform Step 1.
Downgraded-From: =?UTF-8?Q?DISPLAY-local_<NON-ASCII-local@example.com_?=
=?UTF-8?Q?<ASCII-local@example.com>>?=
Downgraded-To: =?UTF-8?Q?DISPLAY-remote1_?=
=?UTF-8?Q?<NON-ASCII-remote1@example.net_<ASCII-remote1@example.net>>?=
Downgraded-Cc: =?UTF-8?Q?DISPLAY-remote2_?=
=?UTF-8?Q?<NON-ASCII-remote2@example.org>?=
Fujiwara Expires August 18, 2008 [Page 10]
Internet-Draft Displaying Downgraded Messages February 2008
Figure 5: Displaying technique 2: Output of Step 1
Then, perform Step 2.
From: DISPLAY-local <NON-ASCII-local@example.com
<ASCII-local@example.com>>
To: DISPLAY-remote1 <NON-ASCII-remote1@example.net
<ASCII-remote1@example.net>>
Cc: DISPLAY-remote2 <NON-ASCII-remote2@example.org>
Figure 6: Displaying technique 2: Output of Step 2
Perform Step 3.
From: =?UTF-8?Q?DISPLAY-local?= <ASCII-local@example.com>
To: =?UTF-8?Q?DISPLAY-remote1?= <ASCII-remote1@example.net>
Cc: =?UTF-8?Q?DISPLAY-remote2?= Internationalized address
=?UTF-8?Q?NON-ASCII-remote2@example.org?= removed:;
Figure 7: Displaying technique 2: Output of Step 3
Perform Step 4. "From", "To", "Cc" header fields are removed in
Figure 8.
Fujiwara Expires August 18, 2008 [Page 11]
Internet-Draft Displaying Downgraded Messages February 2008
Return-Path: <ASCII-local@example.com>
Downgraded-Mail-From: =?UTF-8?Q?<NON-ASCII-local@example.com>?=
=?UTF-8?Q?<ASCII-local@example.com>?=
Downgraded-Rcpt-To: =?UTF-8?Q?<NON-ASCII-remote1@example.net>_?=
=?UTF-8?Q?<ASCII-remote1@example.net>?=
Message-Id: MESSAGE_ID
Mime-Version: 1.0
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 8bit
Subject: =?UTF-8?Q?NON-ASCII-SUBJECT?=
Downgraded-From: =?UTF-8?Q?DISPLAY-local_<NON-ASCII-local@example.com_?=
=?UTF-8?Q?<ASCII-local@example.com>>?=
Downgraded-To: =?UTF-8?Q?DISPLAY-remote1?_?=
=?UTF-8?Q?<NON-ASCII-remote1@example.net_<ASCII-remote1@example.net>>?=
Downgraded-Cc: =?UTF-8?Q?DISPLAY-remote2_?=
=?UTF-8?Q?<NON-ASCII-remote2@example.org>?=
Date: DATE
MAIL_BODY
Figure 8: Displaying technique 2: Output of Step 4
Perform Step 5. (Apply 'Displaying technique 1'.)
Return-Path: <ASCII-local@example.com>
Downgraded-Mail-From: <NON-ASCII-local@example.com>
<ASCII-local@example.com>
Downgraded-Rcpt-To: <NON-ASCII-remote1@example.net>
<ASCII-remote1@example.net>
Message-Id: MESSAGE_ID
Mime-Version: 1.0
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 8bit
Subject: NON-ASCII-SUBJECT
From: DISPLAY-local <NON-ASCII-local@example.com
<ASCII-local@example.com>>
To: DISPLAY-remote1 <NON-ASCII-remote1@example.net
<ASCII-remote1@example.net>>
Cc: DISPLAY-remote2 <NON-ASCII-remote2@example.org>
Date: DATE
MAIL_BODY
Figure 9: Display technique 2: Decoded message
Fujiwara Expires August 18, 2008 [Page 12]
Internet-Draft Displaying Downgraded Messages February 2008
As a result, in this simple example, all original header fields are
displayed in the original form. Differences between Figure 1 and
Figure 9 are Return-Path, Downgraded-Mail-From, Downgraded-Rcpt-To
header fields only.
Author's Address
Kazunori Fujiwara
JPRS
Chiyoda First Bldg. East 13F, 3-8-1 Nishi-Kanda
Chiyoda-ku, Tokyo 101-0065
Japan
Phone: +81 3 5215 8451
Email: fujiwara@jprs.co.jp
Fujiwara Expires August 18, 2008 [Page 13]
Internet-Draft Displaying Downgraded Messages February 2008
Full Copyright Statement
Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Acknowledgment
Funding for the RFC Editor function is provided by the IETF
Administrative Support Activity (IASA).
Fujiwara Expires August 18, 2008 [Page 14]